Inertia operated rate reducer for automatic firearms



J. C. GARAND May 13, 1958 INERTIA OPERATED RATE REDUCER FOR AUTOMATIC FIREARMS Filed Feb. 15, 1954 5 Sheets-Sheet l May 13, 1958 J. c. GARAND 2,834,257

INERTIA OPERATED RATE REDUCER FOR AUTOMATIC FIREARMS Filed Feb. 15, 1954 s Sheets-Sheet 2 INVENTOR. Jul 1311 EL EI'ELTUI'LB.

flTTDR/VEY S May 13, 1958 J. c. GARAND 2,

INERTIA OPERATED RATE REDUCER FOR AUTOMATIC FIREARMS Filed Feb. 15, 1954 5 Sheets-Sheet s IN V EN TOR.

INERTIA OPERATED RATE REDUCER FOR AUTOMATIC FREARMS John C. Garand, Springfield, Mass, assignor to the United States of America as represented by the Secretary of the Army The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to automatic firearms, wherein the firing mechanism is actuated by a reciprocating rod and which embodies a sear locked hammer, and is partieularly directed to a device for reducing and governing the rate of fire thereof.

It has been found in firearms of automatic type, especially in shoulder arms, that the high rate of fire is oftentimes more rapid than is necessary and besides produces undesirable results. For example, the shooter has difiiculty in maintaining the aim of the weapon during a high rate of fire so the efficiency of the weapon is considerably decreased. Further, the weapon is caused to heat up too rapidly.

It is, therefore, the object of this invention to provide in an automatic firearm means for introducing a lapse of timebetween successive shots thereby reducing the rate of fire.

' It is a specific object of this invention to provide in the operating rod mechanism of a gas-operated automatic weapon, a slidable inertia member located between the gas piston and its spring, for retarding the counter-recoil movement of the operating mechanism.

It is another specific object of this invention to prow'de in an automatic firearm a trigger mechanism wherein the sear is actuated by a pivotal inertial member which produces an additional interval between slots.

The specific nature of the invention as well as. other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a side view of the rear portion of an automatic firearm in partial longitudinal section showing the relation of the parts when the operating mechanism is in full recoil position and the trigger is retracted for automatic fire;

Fig. 2 is a side view of the front portion showing the gas cylinder portion of the firearm;

Fig. 3 is similar to Fig. 1 but showing the operating mechanism in firing position;

Fig. 4 is a view similar to Fig. 2, but showing the operating mechanism in firing position;

Fig. 5 is a fragmentary longitudinal cross-sectional View showing-the pivoted inertial member held retracted by the locking device;

Fig. 6 is an enlarged exploded view of the locking device;

Fig. 7 is an enlarged side view partially in longitudinal section of the rear end of the actuator turned 180";

Fig. 8 is a view taken along line 88 of Fig. 1; and

Fig. 9 is a view of the reverse side of the locking member.

Shown in the figures is a rifle of the type of the U. S- Riile, Cal. .39, M1 which has been adapted by the device of this invention to fire automatically at a retarded rate. The rifle is comprised basically of a barrel 12, a gas cylin- 2,834,257 Patented May 13, 1958 der 13 which communicates therewith by means of a gas port 14, an operating rod 15 having a forward tubular portion terminated by an integral piston 16 slidably mounted in the gas cylinder, a receiver 17 fixedly secured to the barrel, a bolt 18 longitudinally reciprocal in the receiver and engaged for actuation by the operating rod, and a trigger housing 19 attached to the lower side of the receiver.

Assembled in trigger housing 19 is a firing mechanism such as is disclosed in U. S. Patent 2,377,388. Included in the firing mechanism is a pivotally mounted hammer 20 which is biased to firing position by a spring 21 and.

is arranged to be actuated to cocked position by engagement of bolt 18 during recoil flight. Hammer 29 is held in cocked position by a pivotal-sear device 22 which is comprised of a primary sear 23, arranged to engage a lug 24 on the forward side of hammer arm 25 when the trigger 26 is in normal forward nonfiring position, and a secondary sear 27 of T configuration which is pivotally mounted to primary sear 23. Secondary sear 27 is arranged to engage, as is hereinafter explained, a lug 28 on the rearward side of hammer arm 25 when trigger 26 is in the firing position and to deliver hammer 20 to primary sear 23 when trigger 26 is permitted to return to the nonfiring position.

Mounted for slidable movement in operating rod 15 is a cylindrical inertia member 29 having similar reduced diameter portions 30 on both ends. Inertia member 29 is reversible in operating rod 15 with one of reduced portions 30 being receivable in a mating well 31, provided in piston 16, and the opposite one of such reduced portions being receivable within one end of a compressible coil spring 32. The opposite end of spring 32 bears against a shoulder (not shown) provided on a rod 36 which is pivotally mounted to the front end of receiver 17 by a pin 34 and which extends forwardly through the interior of spring 32 to prevent buckling thereof when compressed by operating rod 15 during actuation to recoil position. The front end of rod 36 is arranged to be spaced apart from the rear end of inertia member 29 when operating rod 15 is fully recoiled, for purposes to be hereinafter explained.

Pin 34 is mounted in receiver 17 so as to project from one side thereof. Mounted on pin 34 is an actuator rod 38 which extends rearwardly along the side of receiver 17 to a locking device 39. Spaced inwardly from actuator rod 38 and attached thereto by a lateral spacer portion 33 is a vertical connector portion 46] which forms a groove 35 with the top portion of spacer portion 33. Provided in connector 40 is a longitudinal slot 42 which receives pin 3 and permits limited longitudinal movement of actuator rod 38. A tongue portion 37 is provided in the side of receiver 17 to slidably mate with groove 35 and thereby prevent actuator rod 38 from becoming disengaged from pin 34. A lug portion 43 extends upwardly from the front end of actuator rod 38 and is arranged to be engageable by a shoulder 44 on operating rod 15 whereby the actuator rod is movable forwardly until pin 34 is positioned in the rear portion of slot 42 when the operating rod is in battery position.

Locking device 39 is mounted as hereinafter described to a lug portion 45 which depends from the bottom side of receiver 17 and which is provided with a finger 'portion 78 depending from the front side thereof.

Provided in lug 45 is a transverse cylindrical hole 46 in which there: is mounted for'eccentric rotational move ment a drive member 47. Drive member 47 includes a shaft portion 48 and an elongated rectangular head portion 49. A cylindrical portion 50 of larger diameter than shaft 48, and concentric thereto, is arranged adjacent the inner side of head portion 49. Adjacent the inner side of cylindrical. portion 50 is a cylindrical bearing por- 3 tion 51 which is eccentric to the axis of shaft 48 and is adapted to be rotatable in hole 46 whereby drive member 47 is given eccentric movement when rotated.

Mounted on drive member 47 is a lock member 52 which is actuated thereby as hereinafter explained. Lock member 52 includes a substantially rectangular body portion 53 bifurcated to receive lug 45. One of the Walls of body portion 53, noted by 54, is provided with a transverse hole 55 which is arranged to rotatably receive cylindrical portion 58, and the other wall, noted by 56, has a transverse hole 57 which is arranged to rotatably receive shaft 48 whereby rotation of drive member 47 in hole 46 causes eccentric movement also of lock member '52. Extending angularly downward from wall 54 is an arm portion 58 which is terminated by a cam surface 93, having a purpose to be hereinafter described. Protruding upwardly from wall 56 is a lever portion 59 in the rearward side of which is an elongated arcuate hollow portion 76. Extending outwardly from the upper end of lever portion 59 is a fixed pin 66 having a lip portion 98 protruding from the end thereof.

Fixedly secured to the outer end of shaft 48, as by a pin 77, is an indexing member 61 which is spaced from wall 56. Mounted on shaft 48, between indexing member 61 and wall 56, is a loaded coil spring 62 by which rectangular head portion 49 is pressed resiliently into a groove 63 provided in wall 54. Groove 63 is provided with parallel sides 64- which receive the elongated sides of rectangular head portion 49 thcrebetween whereby shaft is positionable in one of two diametrically opposed portions which determine the Automatic" and/or semiautomatic settings of the firing mechanism. T ransfer is made between the two positions by pressing inwardly on indexing member 61 to unseat rectangular portion 49 from groove 63 whereby the indexing member may then be turned to rotate the rectangular head portion into the opposite position.

The end of actuator rod 38, adjacent lock device 39, is provided with an elongated slot 65 which permits the end of pin 60, and lip 90 thereon, to pass therethrough whereby the actuator rod is slidably retained on the pin between the lip and wall 56. Extending inwardly from actuator rod 38, rearwardly of elongated slot 65, are two longitudinally spaced apart lugs 66. Provided in the rear one of lugs 66, on a lower plane than slot 65, is a longitudinal hole 67, which is introduced from the rear end thereof, and a hole 68, which is introduced from the front end thereof and in line with hole 67. A cylindrical passageway 69 of smaller diameter provides communication between holes 67 and 68 and forms a front shoulder 70 and a rear shoulder 71 at the junction of such passageway with such holes. A longitudinal duct 91 in the front one of lugs 66 is aligned with hole 67 and together such holes receive a compressible coil spring 73 which seats against shoulder 70. A headed plunger 74 is inserted rearwardly through spring 73 and passageway 69 and is pressed rearwardly to load the spring. The free end of plunger 74 is then headed, as noted by 75, and the contact of such head portion with shoulder 71 maintains the preload in spring 73. Head 75 is arranged to be reciprocable in hole 67. When actuator rod 38 is installed on pin 69, the front end of plunger 74 is arranged to bear against the upper arcuate side of hollow 76 in lever 59 and away from the longest radii thereof whereby the pin is biased to the front end of slot 65 and actuator rod 38 is biased rearwardly until the bottom side of body portion 53 engages finger portion 78. Further, lever 59 is biased counterclockwise by the pressure of plunger 74 against the upper side of hollow 76 causing arm portion 58 to be biased downwardly.

Provided between trigger 26 and sear device 22 is a vertical slot 79. A pin 80 is arranged to traverse slot 79 and pivotally mounted thereon is an inertial member 81. A flat spring 82 is arranged in slot 79 to cooperate with 4 inertial member 81 for biasing said member in an upwardly clockwise direction, referring to Fig. 1.

Inertial member 81 is comprised of a lower stem portion 83 and a comparatively massive body portion 84. The top of body portion 84 is arranged to project into the path of bolt 18 so as to be moved rearwardly thereby during recoil flight. Provided in the right side of body portion 84 is a channel 85 which forms with stem portion 33 a protruding locking portion 86. When index member 61 is in Automatic position, cam surface 93 of arm portion 58 is arranged to engage locking portion 86 when 'actuator'rod 38 is in rearward position and is arranged to be receivable in channel 85 when operating rod 15, by engagement of shoulder 44 with lug 43, moves the actuating rod forwardly and thereby rotates lock member 52. The rotation of lock member 52 moves arm 53 upwardly causing cam surface 93 thereon to flip inertial member 81 rearwardly against the bias of spring 82 which, when the energy imparted to the inertialmember is overcome, rotates such inertial member forwardly with the arm being received by channel 85.

A suitable symbol is inscribed on indexing member 61 which is so arranged that the symbol is easily seen by.

the shooter when the sear mechanism is set for automatic fire and is hidden from the shooter when the sear mechanismv is set for semiautomatic fire. For semiautomatic fire, drive member 47 is turned by indexing member 61 so I that lock member 52 is moved by the aforedescribed eccenlug 43, and hence cannot be moved by operating rod 15 to actuate arm 58 awayfrom engagement with locking portion 86.

As has hereinbefore been disclosed, secondary sear 27 is essentially of T configuration and is provided with a vertical arm 87 and a longitudinally disposed supporting beam 88 which is pivotally mounted to primary sear 23. Provided on the front side of the upper portion of arm 87 is a hook 89 which, as has hereinbefore been dis closed, is engageable with lug 28 on hammer arm 25 when trigger 26 is in firing position and hammer 20 is in cocked position. The lower portion of arm 87 is arranged to be engageable by inertial member 81 when in forward, normal position whereby secondary sear 27 is rockable by said inertial member to disengage hook 89 from lug 28, freeing hammer 20.

Operation When a firearm which embodies the rate reducing device of this invention is fired, and the sear mechanism is set for automate fire, the exploded gases pass from barrel 12 through gas port 14 to gas cylinder 13 to act on the front end of piston 16 whereby operating rod 15 is driven to its recoil position. As operating rod 15 is driven rearwardly, inertia member 29 therein is likewise driven rearwardly causing spring 32 to be compressed. Inertia member 29 floats freely in operating rod 15 so when the operating rod stops in recoil position, the inertia member continues in flight, disengaging spring 32 from the operating rod, and continues until the increased compression of the spring overcomes the energy imparted to the inertia member.

When the energy in inertia member 29 has been overcome, spring 32 biases the inertia member forwardly, picking up operating rod 15 which has been at rest in recoil position. Thus, a delay has been introduced into the firing cycle'a's the weapon obviously cannot refire until operating rod 15 returns bolt 18 to battery position.

Further, when operating rod 15 was recoiled, bolt 18 actuated hammer 20 to cocked position, engaging lug 28 thereon with. hook 89, of secondary sear 27 and also moved inertial member 81 to its retracted position. When bolt 18 is moved from recoil position by the reengagement of inertia member 29 with operating rod 15, inertial member 81 is permitted to rotate slightly forward until locking portion 86 thereon is engaged by cam surface 93 on arm portion 58 as shown in Fig. 5. As operating rod approaches battery position, shoulder 44 thereon contacts lug 43 on actuating rod 38 whereby the actuator rod is moved forwardly, rotating lock member 52 on drive member 47 causing cam surface 93 to move against locking portion 86, flipping inertial member 81 rearwar l and moving arm portion 58 into position to be received by channel 85. Thus, when spring 82 overcomes the rearward thrust given to inertial member 81, the inertial member is permitted to be biased forwardly by the spring to engage the lower end of arm 87. Whereby, secondary sear 27 is rocked, disengaging hook 89 from lug 28 and permitting hammer to be biased forwardly'by its spring 21 to fire the next round. The rearward flip of inertial member 81 and the reluctance thereof to be moved forwardly by spring 82,

because of the weight of body portion 84, introduces additional delay between the firing of the rounds. t is obvious that any variations in the force moving the recoiling parts of the firearm would normally affect the firing rate thereof. By the device of this invention, such variations vary the energy imparted to inertia member 29 and hence the period of delay of operating rod 15 in recoil position, and the force by which inertial member 81 is flipped rearwardly by the camming action of arm 58 and hence the travel of the inertial member before actuation of secondary sear 27. It is obvious that any increase in the travel of inertial member 81 gives a corresponding increase in the interval of time between shots. As an example, any increase in recoil force during fire, which would normally increase the rate of fire, by the device of the invention increases the interval before the following shot and thereby governs the firing rate. It is obvious that, inversely, a reduction in recoil force decreases the interval before the following shot and thereby proportionately increases the firing rate. Thereby, governing means are introduced-into the firing mechanism of the firearm.

As has hereinbefore been explained, when indexing member 61 is rotated to semiautomatic position, arm 58 is moved downwardly by the eccentric movement of lock member 52 to engage locking portion 86,. holding inertial member 81 in retracted position, and actuator rod 38 is also moved forwardly by the eccentric movement of the lock member to move lug 43 forwardly away from shoulder 44. Thus, the inertial member is held inoperative and the firing mechanism operates conventionally in semiautomatic fire.

It is clearly apparent from the above disclosure that there is here provided a novel device for retarding and governing the rate of fire in automatic firearms which is simple and rugged in construction, positive in operation and is easy to manufacture.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

1. In an automatic firearm having an operating rod reciprocable between a recoil and a battery position, a bolt reciprocable with the operating rod and having a firing pin therein, a firing pin actuating hammer reciprocable between a cocked and a firing position and sear means for releasably holding the hammer in the cocked position, a device for reducing the normal rate of the automatic fire of the firearm including a first inertia means slidingly responsive to recoil movement of the operating rod for delaying the return of the operating rod from the recoil position, and a second inertia means pivotally responsive to battery movement of the operating rod for delaying the release of the hammer by the sear means after the operating rod is in battery position, said second inertia means including a member having a relatively massive body portion and a stem portion extending therefrom mounted to the firearm to provide pivotal movement of said member between a retracting and an actuating position, said member being engageable with the sear means when in said actuating position for release of the hammer, :a spring for biasing said member to said actuating position, and cam means responsive to said battery movement of the operating rod for actuating said member to said retracting position against the bias of said spring for delaying the actuation of the sear means by said member according to the energy imparted to the operating rod by said first inertia means.

2. In an automatic firearm, an operating member actuatable by gas pressure from a battery to a recoil posi,

tion, spring means for returning said operating member to said battery position, inertia means energizable by said operating member during recoil for disconnecting said spring means from said operating member when said operating member reaches said recoil position for delaying the return of said operating member by said spring means to said battery position proportionate to said gas pressure, a bolt actuatable by said operating member, a hammer actuatable by said bolt from a firing to a cooked position, sear means for releasably securing said hammer in said cocked position, a pivotal inertial member actuatable by said bolt from a sear engaging position to a retracted position, said inertial member being cooperaole with said sear means for actuation thereof when said inertial member is in said sear engaging position, a spring for pivoting said inertial member to said sear engaging position, a spring-biased pivotal arm for releasably holding said inertial member in said retracted position, means cooperating with said operating member for actuation of said arm to release said inertial member after the reengagement of said spring means with said operating member andwhen said operating member is adjacent said bait tery position, and a cam portion on said arm engageable With said inertial member for pivoting thereof against the bias ofsaid spring when said arm is actuated'by said operating member for delaying the release of said hammer by said sear means after said operating member is. in said battery position, said delay being proportionate to the force with which said operating member actuates said arm, whereby said inertia means and said inertial member cooperate to reduce and govern the rate of fire of the firearm.

3. In anautomatic firearm, an operating member actuatable by gas pressure from a battery to a recoil position, spring means for returning said operating member from said recoil position to said battery position, an in ertia member positioned between said spring means and said operating member, said inertia member being energized by the recoil movement of said operating member for disengaging said spring means from said operating member when said operating member stops in said recoil position, said inertia member being reengageableby said spring means to said operating rod after a delay proportionate to the energy imparted to said inertia member by said gas pressure, a bolt in engagement with said operating member, a hammer actuatable by said bolt from a firing to a cocked position, a sear device for releasably holding said hammer in said cocked position, a pivotally mounted inertial member engageable with said sear device for actuation thereof to release said trigger, said inertial member being pivotable by said bolt from a sear actuating position to a locked position, a spring for biasing said inertial member to said sear actuating position and for energizing said inertial member to actuate said sear device, a pivotal arm engageable with said inertial member to releasably hold said inertial member in said locked position, rod means cooperating with said operating member and said arm for pivoting said arm to release said inertial member after said operating member is reengaged by said inertia member and is adjacent said battery position, and a cam portion on said arm for pivoting said inertial member against the bias of said spring to a retracted position when said arm is pivoted to release said inertial member, whereby the actuation of said sear device for release of said hammer is delayed after said operating member reaches said battery position a period proportionate to the energy imparted to said inertial member by said operating member through said cam portion, and whereby said inertia and inertial members cooperate to reduce and govern the rate of fire of the firearm.

4. In an automatic firearm having an operating rod reciprocable between a recoil and a battery position, a spring for biasing the operating rod to the battery position, a bolt reciprocable with the operating rod and having a firing pin therein, a firing pin actuating hammer reciprocable between a cocked and a firing position, and sear means for releasably holding the hammer in the cooked position, a'device for reducing the normal rate of the automatic fire of the firearm including a first inertia means 7 energized by the operating rod during recoil movement thereof to slidingly disconnect the spring from the operating rod and delay the return of the operating rod from the recoil position, and a pivotally mounted second inertia means operationally interposed between the operating rod and sear means for actuation by the operating rod when adjacent battery position to subsequently actuate the sear means to release the hammer after a delay relative to the mass of second inertia means.

5. In an automatic firearm having an operating rod reciprocable between a recoil and a battery position, a spring compressible by the operating rod when moving from battery to recoil position for returning the operating rod to the battery position, a bolt reciprocable with the operating rod and having a firing pin therein, a firing pin actuating hammer reciprocable between a cocked and a firing position and sear means for releasably holding the hammer in the cocked position, a device for reducing the normal rate of the automatic fire of the firearm including a first inertia member slidingly interposed between the operating rod and the spring for energization by the operating rod during movement thereof from the battery position to the recoil position to disconnect the spring from the operating rod a period of time proportionate to the energy imparted to said first inertia means by the operating rod, a pivotally mounted second inertia means normally engaged withv the sear means for actuation thereof to release the hammer, cam means actuatable against said second inertia means by the operating rod when adjacent battery position for pivoting said second inertia means away from normal position, and a relatively masive head portion on said second inertia means for delaying through the inertia thereof the return of said second inertia means to normal position.

6. In an automatic firearm having an operating rod reciprocable between a'recoil and a battery position, a hammer and sear means for releasably holding the hammer in a cocked position, a device for reducing the normal rate of the automatic fire of the firearm including an inertia member having a relatively massive body portion and a stem portion extending therefrom, pin means eX- tending through said stem portion for mounting said inertia member for pivotal movement between a retracting and an actuating position, cooperating surfaces on said inertia member and the sear means enga'geable when said inertia member is adjacent actuating position for actuating the sear means to release the hammer, a spring for biasing said inertia member to the actuating position, and cam means actuated by the operating rod when adjacent battery position and disposed for engagement with said inertia member for actuation thereof to the retracting position against the bias of said spring for delaying the actuation of the sear means by said inertia member relative to the energy imparted thereto by the operating rod and the inertia of the mass of said body portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,431,057 Sutter -1 Oct. 3, 1922 1,532,305 Darne Apr. 7, 1925 1,573,655 Sutter Feb. 16, 1926 2,451,624 Loomis et a1 Oct. 19, 1948 2,459,158 Garand Jan. 18, 1949 2,715,355 Garand Aug. 16, 1955 2,748,661 Simpson June 5, 1956 

